Method for extruding a profile or a similar billet from a bolt or bar and corresponding device

ABSTRACT

A method for extruding a profile or a similar billet from a bolt or bar that is guided in a recipient bore of a recipient and that is extruded by an extrusion die through a shaping section of a shaping tool. Once the front face of the bar is placed on the rear surface of a preceding bar, air or similar flowing agents present on the surfaces are discharged during pressure build-up in an approximately radial relation together with the contaminations that are present in detached form on the transversal bur surface. During pressure build-up, parts of the transversal burs are radially displaced; the displaced parts of the traversal bur surface are discharged on the periphery in an approximately radial relation before the bar enters the shaping tool. To achieve this, a welding chamber or pre-chamber is disposed in the direction of extrusion (x) in a gap that can be adjusted between the recipient and the shaping tool. The chamber is provided with at least one lateral opening or discharge channel through which the displaced parts of the transversal bur are discharged.

BACKGROUND OF THE INVENTION

[0001] The invention concerns a process for extrusion molding of a profile or similar billet from a bolt or bar which is guided in a receiver bore of a receiver or holder and extruded by means of an extrusion die in the extrusion direction through a molding cross section of a molding tool. Preferably, before entering the mould cross section, the front face of the bar is moved in the extrusion direction up to the rear face of the preceding bar, and the connection area of the bar ends resulting under pressure—namely compression and forming pressure—is then brought to the mould cross section. The invention also concerns a device which is particularly suitable for this with a molding tool which is axially movable relative to the holder and can be adjusted and fixed in its spacing therefrom.

[0002] In extrusion molding the ductile material of a heated casting bar, which is preformed in the metal working area from non-ferrous or sintered metal or steel but in particular an aluminium alloy, or the roll bar section, is extruded by a die—or for hydrostatic extrusion molding by means of a fluid—through one or more mould cross sections of a molding tool which are positioned transverse to the extrusion direction. In direct or forward extrusion, the die moves in the processing direction of the resulting profile to the mould cross section; in indirect or reverse extrusion, the material is extruded against the die direction through a tool which is fixed on the hollow die.

[0003] When for example in direct extrusion the face of the die in the extrusion direction has reached the molding tool, between the two, at the rear tool surface, there remains an extrusion residue of the compressed bar as a more or less disc-like structure. This is usually removed by a cutter which is moved radial to the tool before the following bar—pushed by the now retracted die in the holder—contacts the tool surface and the actual molding process can continue.

[0004] Metals bars, in particular those made of aluminium alloys, are coated with contaminants—for example lubricant residue—and an oxide layer. Above all the oxide particles at the bar face have proved extremely harmful for the structure of the resulting profile; the zone they produce with contaminating inclusions—also known as the transverse extrusion seam—is relatively long depending on the profile form and extrusion speed, and as quality requirements increase, leads to ever longer profile sections having to be discarded from the resulting extrusion with all resulting consequences of falling profitability with shrinking profile output; when the new bar is extruded, a transverse extrusion seam is created between this and the metal remaining in the tool inlet. This can be found in the extruded profile billet in the form of a tongue. The quality of the transverse extrusion seam depends on the tool design and the “clean” working method during extrusion, but cannot be measured in the profile bar without destroying this. Therefore, in profiles which are subject to mechanical stress, the transverse extrusion seam zone of varying length must be cut away from the extruded profile billet.

[0005] In order to reduce the contamination areas—the transverse extrusion seam referred to above—occurring in extrusion moldings, in particular of aluminium alloys, at the transition of two adjacent blocks or bars, DE 196 05 885 C1 by the applicant proposes that before entry of the front bar end into the mould cross section, this bar be moved in the extrusion direction out of the holder by a slight projection extent in order to cut off and remove the resulting disc-like section of the free bar end and then bring this up to the mould cross section or the rear end of the previous extruded bolt. By removing this front section, its oxide skin or similar contamination is removed so that—assuming rapid contact of the now almost virgin face of the bar on the tool—contamination from oxide particles on this bar face can be reduced and the occurrence of lengthy discards in a profile billet avoided as far as possible.

[0006] In order now to reduce the time gap between the cutting process and the start of further extrusion, removal of the bar face should take place at approximately the same time as the other trimming of the extrusion residue from the tool. The holder at the end of its extrusion process should be moved axially away from this; when its adjacent faces are attached to each other, the cutting process for the extrusion residue and bar can begin. The two cut surfaces are joined together after only slightly more than ten seconds during the extrusion process. This means that the cut surfaces oxidise to a minimum and largely virgin material surfaces are joined in the transverse extrusion seam as a condition for the production of good transverse extrusion seams.

[0007] The device presented in the said DE 196 05 885 C1 for performance of this process offers a cutter with two spaced cutting blades which are guided simultaneously in a radial movement path over the opening of the receiver bore and the rear surface of the tool.

[0008] It has, however, now been found that the cut surfaces—for example due to the increasing adhesion of minute aluminium residues on the cutter blade—have an undefined roughness. When the cut surfaces are extruded together, air can be enclosed in the grooves of the corrugations, preventing the virgin surfaces from meeting and the possibility of a good weld joint over the entire transverse extrusion seam contact surface.

[0009] In view of this prior art, the inventors have faced the objective of further improving the process described initially—including a device for this—and excluding the transverse extrusion seam as a source of faults between the two joined bar ends.

SUMMARY OF THE INVENTION

[0010] The foregoing object is achieved by the present invention by providing a process for extrusion molding of a profile or similar billet from a bolt or bar, which is guided in a receiver bore of a receiver or holder and extruded by means of a extrusion die in the extrusion direction (x) through a mold cross section of a molding tool, where preferably before entering the mould cross section, the front face of the bar is moved in the extrusion direction (x) to the rear surface of a preceding bar and the connection area of the bar ends resulting under pressure is then brought to the mould cross section, characterised in that after contact of the front face of the one bar on the rear face of the preceding bar, air or similar fluid media present at these surfaces together with contaminants dissolved between them at the transverse extrusion seam surface is/are expelled approximately radially during the pressure build-up. The invention further comprises a device for extrusion molding of a profile or similar billet from a bolt or bar, which is guided in a receiver bore of a receiver or holder and by means of an extrusion die extruded in the extrusion direction (x) through a mold cross section of a molding tool which is axially movable in relation to the holder and can be fixed and adjusted in distance (n) therefrom, in particular for performance of the process according to any of the previous claims, characterised in that in the gap, which is adjustable between the receiver or holder and the molding tool, is arranged a welding or prechamber and this is fitted with at least one side aperture or discharge channel.

[0011] According to the invention, after placing the face of the one bar on the rear surface of the preceding bar, air or similar fluid media present at these surfaces with the contaminants dissolved between them at the transverse extrusion seam surface can be dissipated approximately radially during the pressure build-up. Advantageously, on pressure build-up, parts of the transverse extrusion seams are displaced radially.

[0012] According to a further feature of the invention the displaced parts of the transverse extrusion seam surface are dissipated approximately radially at the periphery before entry of the bar into the molding tool; due to the pressure build-up, from parts of the transverse extrusion seam surface at least one radial billet is formed and discharged at the side. According to the invention this can then be cut off and its flow path closed again before the actual extrusion process begins. This process provides a targeted unlimited transverse extrusion until only a transverse extrusion seam surface without air inclusions enters the profile extrusion. The continued extrusion process is performed as part of the invention under the exclusion of atmospheric oxygen. This measure also eliminates cases of residue in which transverse extrusion into limited volume catchment pockets is not sufficient and residue of the transverse extrusion seam surfaces contaminated with air can enter the profile extrusion.

[0013] The invention concerns a device which should be used above all to perform the process described above and in which, in the adjustable gap between the receiver or holder and the molding tool in the extrusion direction, a welding or prechamber is located from which at least one aperture or discharge channel leads away approximately radially. Allocated to the opening of such a discharge channel and straddling this is a cutting blade of a cutter.

[0014] Here it has proved favourable to arrange the welding or prechamber in a tubular housing and in this preferably provide two approximately radial discharge channels on a common axis; this arrangement requires only one cutter with two cutting blades; the latter run parallel to each other in a U-shaped cross section of the cutter. At the end of the cutting process the cutter blade spans its allocated opening in a sealing manner and remains there throughout the entire subsequent extrusion process.

[0015] This device also contains a type of transverse extrusion seam welding chamber to be inserted between the die and receiver or firmly attached to one of these two components, with side apertures or discharge channels for transverse extrusion. The side apertures can have any shape in order to expel the contaminated transverse extrusion seam surface safely from the area of the extruded product volume; when evidently sufficient extruded product volume has been expelled transversely, during the extrusion process the billets emerging at the side are cut by the cutter which then seals the side apertures or apertures of the discharge channels of the transverse extrusion seam prechamber. When this closing process has been performed and hence the transverse extrusion stopped, the actual extrusion process begins under air exclusion. Thus, extrusion into the transverse extrusion seam prechamber continues until immediately before the side outlet openings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Further advantages, features and details of the invention arise from the following description of preferred embodiment examples and with reference to the drawing;

[0017]FIGS. 1 and 3: show a longitudinal section through a sketched holder or receiver of an extrusion press with an extrusion die which is arranged in front of the bolts or bars in the extrusion direction and a tool following at a distance;

[0018]FIG. 2: shows an axial view of the receiver of the extrusion press after cutting a face disc of the bolt or bar;

[0019]FIG. 4: shows the longitudinal section through the holder with the tool at its receiver face;

[0020] FIGS 5 and 6: show two further longitudinal sections through a receiver with different forms of bolt;

[0021]FIG. 7: shows a horizontal longitudinal section through an arrangement according to the invention of an extrusion press with prechamber;

[0022]FIG. 8: shows a cross section through the arrangement in FIG. 7;

[0023]FIG. 9: shows an oblique view of an extrusion residue.

DETAILED DESCRIPTION

[0024] An extrusion press, not shown, for direct extrusion molding of profiles according to FIG. 1 has on an extrusion cylinder an extrusion die 10 which runs in the longitudinal axis A of a bore 16 passing through a receiver or holder 14. The diameter d of an extrusion disc 12 on the holder-side free face of the extrusion die 10 is slightly shorter than the free bore diameter so that the extrusion die 10 can be introduced into the receiver bore 16. The said free bore diameter can where applicable be bordered by the inner face of a receiver sleeve inserted in the holder 14 or its bore 16 and omitted in the drawing; in this case the interior of this receiver sleeve is known as the receiver bore 16.

[0025] The maximum distance between a die-side receiver front 18 and the extrusion disc 12 in the rest position, not shown, of the extrusion die 10, is dimensioned such that placed before the receiver bore 16 is a bolt or bar 30 of alloy, in particular of a preheated aluminium alloy, which can be pushed into this receiver bore 16 by the extrusion die 10 in the extrusion direction x.

[0026] From the receiver face 20 lying remote from the extrusion die 12, at a radial distance a from the peripheral edge 17 of the receiver bore 16 protrudes a molding ring 22 with radial surface 23 which borders the pocket 24 directed towards the longitudinal axis A. Although the drawing shows a moulded ring 22 of rectangular cross section protruding from the receiver face 20, this attachment or its surface 23 can also have a different shape in further embodiments. This also applies to an attachment on the rear receiver front 18; in the drawing the receiver bore 16 surrounds a ring collar 26 directly connected to its edge 17.

[0027] At a distance n from the receiver face 20, in a swage holder, not shown, rests an axial multipiece swage 38 as a molding tool with flat molding dish 42 made in its holder—side tool surface 40 and of depth b and a contour corresponding for example approximately to the receiver bore 16, and with a discharge channel 44 running in the extrusion direction x through which is expelled a billet 50 created in a molding cross section 46 of the swage 38. The contour of the molding dish 42 holding a disc-like molding 52 connected with the billet 50 is selected so that it contains all inlets of the tool 38 running in the extrusion direction x and not shown in the drawing for reasons of clarity.

[0028] Above the longitudinal axis A in FIG. 1, on the receiver face 20 can be seen a lifting device 54 for a cutter knife 56 which is provided to be movable radially into a gap 28, determined by distance n, between the holder 14 and swage 38.

[0029] During the extrusion process the bolt or bar 30 is extruded through the molding tool 38 and thus forms the billet 50 starting from the disc-like molding 52; the molding 52 forms in the molding dish 42 described above of the swage 38 and is of one piece with an extrusion residue 60 of thickness e protruding from the tool surface 40 against the extrusion direction x; this is created during the extrusion process in the die-free face end area of the receiver bore 16 when the holder 14 is retracted against the extrusion direction x. The surface 23 of the molding ring 22 at the receiver face 20 then stands as a stop face parallel to this at that distance n from the tool surface 40. The holder 14 and swage 38 are temporarily fixed in this position to allow a subsequent cutting process.

[0030] A new block or bar 30 is placed before the extrusion residue 60 and the surfaces of the block or bar 30 and extrusion residue 60 to be allocated to each other are cut away in order to improve the quality of the billet 50 in this area. Between the metal remaining in the inlets of tool 38 and the new bar 30 is created a transverse extrusion seam.

[0031] For this, by simultaneously lowering two cutting blades 58, 58 _(a) of the cutter 56 indicated in FIG. 1, the extrusion residue 60 and a face disc 32—determined by the protrusion of the bar 30—of thickness f of the bar 30 and its face 34 pointing in extrusion direction x are removed; at the bar face 34, before the procedures described here, an oxide layer or similar contamination has formed, of which the oxide particles, air or dirt inclusions would, if included in the resulting billet 50, form the said disruptive contaminants. The result is cut surfaces 36 and 62 (FIG. 2, 3) facing each other which can then be heated by a cutting blade 56, brought to a high temperature and shaped so as to achieve the desired cutting form, during the cutting process over a heating time to be selected for which the cutting blade 56 makes contact with the transverse seam extrusion surface. The resulting cut surfaces 36 and 62 can be joined together after just 10 to 15 seconds.

[0032] Instead of or in addition to the use of heated blades 58, 58 _(a), it is also possible after the cutting process according to FIG. 3 and between the opposing cutting surfaces 36, 62 to insert a heating device 64 with bilateral heating source 66—for example a high performance gas burner 64 with flame points 66—radially into the gap 28 in order to heat the transverse extrusion seam or cut surfaces 36, 62 before they are joined together under pressure and thus displace the contaminated surface for the transverse extrusion seam sideways from the welding area to be used; the parts of the transverse extrusion seam surface are then discarded radially into the holder pocket 24 on the molding ring 22.

[0033] By shaping the cut surface 36 of the bolt or bar 30 with simultaneous use of suitable extrusion parameters—such as a temperature profile over the bolt length t, t₁,—after joining together the cut surface pairs, in the subsequent pressure build-up the air is expelled outwards to the side and/or along the bolt surface to the extrusion disc 12 and simultaneously the minimally oxidised or contaminated surface for the transverse extrusion seam is torn away.

[0034] On the swage side a closed cutting surface 62 aligned to the tool surface 40 is produced due to correspondingly designed material inlet openings in the swage 38 and a suitable cutter geometry. In order to allow the sideways outlet of air, in the receiver face 20 are produced grooves, not shown in the drawing, through which the air can be discharged but no extruded product can escape.

[0035] The treatment of the said surfaces forming the transverse extrusion seam, as well as the said temperature increase, consists of a particular shaping of the cut surfaces facing each other; thus for example the cut surface 36 _(a) according to FIG. 5 is formed in the shape of a pitched roof with radial horizontal ridge burr 35, the cut surface 36 _(b) in FIG. 6 in longitudinal section as a flat part ellipse. The state shown here also concerns a first extrusion step in which pressure has built up; radial outflow of the metal leads to a peripheral ring edge 37.

[0036] On performance of the extrusion process described, after each extrusion process by expelling the extrusion residue 60 and the subsequent extrusion residue cutting process, a type of self-cleaning of the extrusion press can take place and additional contamination procedures avoided.

[0037] The air which is enclosed during the immersion process connecting the axially opposing cut surfaces 36, 36 _(a), 36 _(b), and 62 must, as already stated, preferably be able to escape radially, where applicable however also between the surfaces of the bar 30 and the receiver bore 16 towards the extrusion disc 12. Here the bolts 30 are heated with a temperature profile such that the bolt rear surface 33 which is forged to the extrusion disc 12 is colder than at the bolt face 34 pointing towards the swage or tool 38. For this, at the periphery of the fixed—or where applicable also detached—extrusion disc 12 air outlet grooves must be provided which are indicated merely individually with 11 in FIG. 4.

[0038] In FIG. 7, between the holder 14 and the swage 38 is inserted a tube 68 as a housing for a welding or a prechamber 70 of diameter i of approximately 560 mm in which the face 34 _(a) of the advanced bolt 30 contacts the rear surface 33 _(a) of the previously formed bolt 30 _(a). The rear surface 33 _(a) and front surface 34 _(a) can where applicable also be considered cut surfaces if in particular cases they result from a cutting process.

[0039] So that only the part of the said transverse extrusion seam surface forming a clean welding seam and free from air inclusions can enter the billet 50, in the pipe or housing 68 are provided radial apertures or outlet channels 72, the common axis Q of which in the embodiment example shown crosses horizontally the longitudinal axis A of the receiver bore 16. Thanks to these side apertures 72 the contaminated transverse extrusion seam surface is extruded out of the area of the extruded product volume as a transverse extrusion billet in transport direction y. If in this way sufficient extruded volume is output in the form of the laterally emerging billet 31, the latter can be cut off during the extrusion process by a cutter 57 which is approximately U-shaped in cross section and arranged on a lift device 54 and the longitudinal axis B of which crosses the transfer direction y. The cutter blades 59 of cutter 57, formed by the two legs of the U, after the cutting process close the openings 74 of the side apertures 72 as shown in FIG. 8.

[0040] After closing the apertures 72—which interrupts the transverse extrusion process—the actual extrusion process is carried out under air exclusion. The bolt 30 _(a) is expelled until its bolt rear surface 33 according to FIG. 7 stands directly in front of the side apertures 72. The extrusion die 10 with its fixed extrusion disc 12 and the air evacuation facilities indicated in FIG. 4 is then retracted and the new bolt 30 for the next extrusion process is loaded without an extrusion residue occurring; the extrusion residue remaining in the welding or prechamber 70 is expelled with parts of the face 34 _(a) of the new bolt 30, the contaminated transverse extrusion seam surface, from the welding or prechamber 70 as described.

[0041] From the expelled billet 31 the cutter 57 cuts off extrusion residue 31 _(a) which is easily extracted from the extrusion press. A bar-like extrusion residue 31 _(a) thus created—which in another embodiment can also be round in cross section—has according to FIG. 9 for example a height h of 200 mm and a thickness q of 70 mm. These extrusion residues 31 _(a) can perhaps be supplied to a remelting plant. 

1-19. (cancelled)
 20. A process for extrusion molding a profile from a plurality of bars, comprising the steps of: providing a holder (14) having a receiver bore (16); providing a molding tool (38) downstream, with respect to the extrusion direction (x), of the holder, wherein the molding tool includes a mold cross section (46); feeding at least a first (30) and a second (30 a) bar axially to the mold cross section wherein the rear face (32 a) of the first feed bar and the front face (34 a) of the second feed bar are brought into contact upstream of the mold cross section resulting in a pressure build-up at the contacting faces of the first and the second bar; and removing radially fluid media and contaminants from the contacting faces during pressure build-up.
 21. A process according to claim 20, wherein the contacting faces form a transverse extrusion seam and, on pressure build-up, parts of the transverse extrusion seam are displaced radially.
 22. A process according to claim 21, wherein the displaced parts of the transverse extrusion seam are discharged approximately radially at the periphery before entry into the molding tool.
 23. A process according to claim 22, wherein the displaced parts form at least one radial billet (31) which is discharged approximately radially.
 24. A process according to claim 23, wherein the radial billet (31) is cut away and its flow path (72) closed.
 25. A process according to claim 24, wherein the radial billet (31) is cut away prior to extruding in the molding tool.
 26. A process according to claim 20, wherein the extrusion process is performed under air exclusion.
 27. A process according to claim 26, wherein the radial billet (31) is expelled through a radial discharge channel (72).
 28. A device for extrusion molding a profile from a plurality of bars, comprises: a holder (14) having a receiver bore (16) for receiving the bars; a molding tool (38) downstream, with respect to the extrusion direction (x), of the holder; means for moving one of the holder and the molding tool axially relative to the other in the direction (x) for adjusting a gap (n) therebetween; and a prechamber (70) locating the gap (n), said prechamber having a discharge channel (72).
 29. A device according to claim 28, wherein the prechamber (70) is bordered by a tubular housing (68) in which is arranged at least one approximately radial discharge channel (72).
 30. A device according to claim 29, wherein the prechamber (70) has a diameter (i) which corresponds to that of the receiver bore (16).
 31. A device according to claim 29, wherein at least two approximately radial discharge channels are provided on a common axis (Q) in the housing (68) of the prechamber (70).
 32. A device according to claim 28, wherein a cutter (57) is arranged outlet opening (74) of the discharge channel (72).
 33. A device according to claim 28, wherein the prechamber (70) is firmly connected to one of the receiver (14) and the molding tool (38).
 34. A device according to claim 32, wherein the prechamber has a plurality of outlet openings (74) and, allocated to each opening (74) is a cutting blade (59) of a cutter (57).
 35. A device according to claim 34, wherein the cutter is a U-shaped cutter (57) having at least two parallel cutting blades (59).
 36. A device according to claim 32, wherein the cutting blade (59) of the cutter (57) span the opening (74) in a sealing manner.
 37. A device according to claim 32, wherein the cutter (57) is displaceable transverse to the longitudinal axis (A) of one of the receiver bore (26) and the prechamber (70).
 38. A device according to claim 32, wherein the cutter (57) is rotatable through 90° about its longitudinal axis (B). 